Winches are commonly used to lift a load with a line, wherein such winches of which we are aware may include an arrangement of pulleys around which the line is wrapped to provide a predetermined mechanical advantage ratio. The pulleys are moved towards and away from each other by means of a piston and cylinder arrangement. The interaction of such a piston and cylinder arrangement with the pulley assembly in known devices results in a complex and expensive to manufacture structure.
It is accordingly an object of the present invention to provide a pneumatic or hydraulic winch of a block and tackle type construction which has relatively few moving parts, is therefore simple in design, and capable of reliable operation in rugged and hostile environments.
Another object is to provide a pneumatic winch wherein the pulley assembly is located within a working area of a piston and cylinder arrangement to achieve a substantially even distribution of operating forces during operation of the winch which wall result in a stronger and safer device.